In radio communication technologies, blocking and interference are some of the main system killers. They can for example occur when an interfering signal, having a center of frequency different from the desired signal carrier frequency is very strong.
Many receivers, such as for wideband radio, employ a so-called Automatic Gain Control (AGC) mechanism for regulating the dynamic range of the received signals, for example in order to prevent saturation of the receiver when a strong signal is present. The received signal power can be measured at a suitable location in the receiver and the gain of a Variable Gain Amplifier (VGA) may then be controlled based on the power measurements. In particular, the AGC mechanism provides means to temporarily reduce the gain of a variable amplifier in case strong interfering signals are received.
However, when the AGC mechanism is turned on or off, or when a gain adjustment is effectuated, unwanted transient signals are generated. These transients can be highly energetic, and introduce non-linear distortions, commonly called glitches, in the useful part of the desired signal. The desired signal is thereby heavily distorted and a number of samples of the digital received signal are corrupted. The result is a loss of link performance. When the code rate is very high, just a few bit errors will result in block or frame errors, and the performance loss in terms of block or frame error rates can be very large. Glitches also affect voice services, and they also result in some performance loss.